Full text of "USPTO Patents Application 10695194"

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(12)

UK Patent Application n 9 >GB < >2 360 089 «3>A

(43) Date of A Publication 12.09.2001

(21) Application No 0005633.8

(22) Date of Filing 10.03.2000

(71) Appticant(s)

Universrte da Geneve

(Incorporated in Switzerland)

Rue General-Dufour 24, Case Postele, CH-1211.

GENEVA 4, Switzerland

(72) Inventor(s)

Jean- Charles Sanchez
Dents Francois Hochstasser

(74) Agent and/or Address for Service
Lucas & Co

135 Westhall Road, WARUNGHAM. Surrey, CR6 9HJ.
United Kingdom

(51) INT CL 7 tM

G01N 33/543 , C07K 14/47 14/775 . G01N 33/577 33/68

(52) UK CL {Edition S )

G1B BAE B103 B309 B403 B500

(56) Documents Cited

EP 0861900 A WO 98/45440 A WO 98/23962 A
Mol. Cell. Biochem.; Vol 198(1&2). PP 69-78 (1999). Pu
et aL J. Neurochem.; Vol 66 (4), pp 1648-1656 (19961.
Myers-Payne etal

(58) Field of Search

UK CL (Edition R ) GIB BAE

INT CL 7 C07K 14/47 14/775 , G01N 33/543 33/577
33/68

ONLINE: JAPKX WPt, EPODOC, TXTE, MEDUNE,
EM8ASE, SCISEARCH, BIOSIS, CAPLUS

(54) Abstract Title

Diagnostic assay for transmisible spongiform encephalopathies

(57) Heart and brain fatly acid binding proteins (H-FABP, B-FABP) are markers for TSEs especially CJD. The

ZJZ* ro^des a diagnostic assay for either of these markers, preferably by enzyme

sr^cific antibody thereto Since H-FABP is also a marker for acute myocard*! infarction (AMI) to distinguish

SS Tom A^e^es an assay specific to AMI, e.g. using troponin-1 or CK-MB as a marker, also to be earned

out.

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2360089

"DIAGNOSTIC ASSAY FOR TRANSMISIBLE SPONGIFORM
ENCEPHALOPATHIES"
BACKGROUND OF THE INVENTION
Field of the Invention
5 This invention is in the field of diagnostic assay

using a protein or an antibody thereto.
Description of the related art

Transmissible spongiform encephalopathies (TSEs) are
neurodegenerative diseases of the central nervous system.

10 They can be transmitted, inherited or occur sporadically
and are observed in animals, e.g. as bovine spongiform
encephalopathy in cattle or scrapie in sheep, as well as
in humans as Creutzfeldt- Jakob disease (CJD) , Gerstman
Straussler Scheinker syndrome, Fatal Familial Insomnia or

15 Kuru. They have a long incubation period, leading to
ataxia, dementia, psychiatric disturbances and death.
Neuropathological changes include vacuolar degeneration
of brain tissue, astrogliosis and amyloid plague
formation. The diseases are difficult to diagnose pre-

20 mortem.

The cerebrospinal fluid (CSF) of CJD patients
displays two additional polypeptide by two-dimensional
polyacrylamide gel electrophoresis [Harrington, M.G. New
England Journal of Medicine 315, 21$ (1986), Hsich, G. ,

25 Kenney, K. , Gibbs, C. J. , Lee, K.H. & Harrington, M. B.
New England Journal of Medicine 335, 924 (1996).] The
function of these 14-3-3 polypeptides remain unclear in
TSE. They can be used in a pre -mortem test for CJD
diagnostic evaluation, but have low specificity.

30 Monoclonal antibodies to the abnormal form of prion

protein are available and can be used in an enzyme -linked
immunoassay, as described in PCT Specifications WO
98/23962 and 98/32710 and Schmerr, M. J. , the Beckman

Coulter Pace Setter Newsletter 3(2) ,1-4 (June 1999), but
these procedures have not yet been fully developed.

Development of new non-invasive blood CJD and BSE
markers would help clinicians to establish early
diagnosis .

SUMMARY OF THE INVENTION

It has now surprisingly been found that two fatty
acid binding proteins (FABP) , known as heart (H-FABP) and
brain (B-FABP) , are markers for TSEs . Thus, a TSE or the
possibility thereof in a sample of body fluid taken from
a patient suspected of suffering from the TSE, which
comprises determining the concentration of heart or brain
fatty acid binding protein (H-FABP or B— FABP) in the
sample. the method is especially applicable to the
diagnosis of CJD in human patients.

Conveniently the method is carried out using an
antibody to H-FABP or B-FABP, whereby the extent of the
reaction between the antibody and the FABP in the sample
is assayed and related to the concentration of FABP in
the sample. The concentration thus determined is used to
make or assist in making a diagnosis.

The present invention enables an assay of high
sensitivity, specificity and predictive accuracy for CJD
to be carried out. "Sensitivity" is defined as the
percentage of true positives given by the assay on
samples taken from patients in whom clinical examination
has confirmed CJD. "Specificity" means the percentage of
true negatives given by the assay on control samples,
i.e. from patients in whom clinical examination has not
revealed CJD. "Predictive accuracy" means the ratio of
true positives to total positives (true + false)
expressed as a percentage .

H-FABP is a known marker of acute myocardial
infarction (AMI), see Ishii, J\ et a2., "Serum

- 3 -

concentrations of myoglobin vs human heart- type
cytoplasmic fatty-acid binding protein in early detection
of acute myocardial infarction" , Clinical Chemistry
1997; 43 1372-1378. Therefore, in order to use an assay
5 for H-FABP for the diagnosis of COD in humans to better
advantage, it is desirable to perform another kind of
assay for AMI (one in which the marker is not a FABP) in
order to eliminate from the diagnosis for CJD those
patients who are positive in the AMI assay.

10 Thus, in a particular embodiment, the invention

provides a method which comprises determining the
concentration of H-FABP in a first assay, as defined
above, whereby a positive result indicates either a CJD
or acute myocardial infarction, and which further

15 comprises carrying out a second diagnostic assay, for
acute myocardial infarction (AMI) only, whereby a
positive result in the H-FABP assay and a negative result
in the assay for AMI indicates that the patient might be
suffering from CJD. Assays using Troponin- 1 and Creatine

20 Kinase-MB (CK-MB) as early biochemical markers of acute
myocardial infarction (AMI) are well known and suitable
for the above purpose.

A similar H-FABP and also a brain-specific fatty
acid binding protein (B-FABP) have been found in the

25 brain of mice, see Pu , I-. et al. , Molecular and Cellular
Biochemistry 198, 69-78 (1999) . Brain H-FABP (not to be
confused with B-FABP) is believed to differ from heart H-
FABP by a single amino acid substitution. However, B-
FABP differs considerably. Sellner, P. A. et al., "

30 Development role of fatty acid binding proteins in mouse
brain" Dev. Brain Res. 89, 33-46 (1995), estimated the
DNA homology at 69%, while A. Schreiber et al. ,
"Recombinant human heart-type fatty acid binding protein
as standard in immunochemical assays", Clin. Chem. Lab.

- 4 -

Med. 36(5) , 283-288 (1998), mention 64% amino acid
sequence homology and that a monoclonal antibody to human
H-FABP is cross-reactive with human B-FABP to the extent
of only 1.7%.

5 Now that the present inventors have found that H-

FABP is a marker for C JD , it is a very reasonable
prediction that B-FABP will also be. Since B-FABP is
specific to brain tissue and does not appear to react
significantly with a monoclonal antibody to H-FABP , it

10 will not give positives for AMI , making a separate assay
for AMI unnecessary.
BRIEF DESCRIPTION OF THE DRAWINGS

The Figure is a graphic representation on the y-axis
of H-FABP concentration represented by optical density

15 measurement at 405 run , as determined by the method of the
invention , for (a) a control group having neither CJD nor
AMI (b) a group having AMI and (c) a group having CJD.
DESCRIPTION OF PREFERRED EMBODIMENTS

For the method of assay, the sample can be taken

20 from any convenient body fluid of the subject. The
method is considered applicable to all types of TSE ,
including those referred to above , and to any human or
animal suffering therefrom. The marker , H-FABP or B-
FABP, is preferably measured by an immunoassay, using a

25 specific antibody to H-FABP and measuring the extent of
the antigen (H-FABP or B-FABP) /antibody interaction- For
the diagnosis of human patients , the antibody is
preferably anti-human H-FABP or B-FABP . Similarly, if the
patient is an animal the antibody should be to the H-FABP

30 or B-FABP of the same animal variety , e.g. an ti -bovine H-
FABP or B-FABP if the patient is bovine. It may be a
monoclonal antibody or an engineered antibody.
Conveniently a mouse anti-human, anti-bovine etc.
(depending on the animal from which the sample to be

- 5 -

bested has been derived) monoclonal antibody is used.
Antibodies to H-FABP are known, e.g. 66E2 and 67D3
described by Roos, W. et al. , "Monoclonal antibodies to
human heart type fatty acid-binding protein" , J. Immunol.
5 Methods 133 149-153 (1995) . Antibody 66E2 is

commercially available. Also, the usual Kohler -Mil stein
method may be used to raise H-FABP or B-FABP antibodies.
The source of protein for this purpose can be the
naturally derived or recombinant DNA-prepared protein .

10 Recombinant human H-FABP and B-FABP have been described
by Schreiber, A. supra and Shimizu, F. et al. ; "Isolation
and expression of a cDNA for human brain fatty acid
binding protein (B-FABP)", Biochim Biophys. Acta 1354,
24-28 (1997) , respectively. Less preferably, the

15 antibody may be polyclonal .

Any known method of immunoassay may be used. A
sandwich assay is preferred. In this method, a first
antibody to the FABP is bound to the solid phase such as
a well of a plastics microti tre plate, and incubated with

20 the sample and with a labelled second antibody specific
to the H-FABP or B-FABP to be detected. Alternatively, an
antibody capture assay could be used here, the test
sample is allowed to bind to a solid phase, and the anti-
FABP antibody is then added and allowed to bind. After

25 washing away unbound material, the presence or amount of
antibody bound to the solid phase is determined using a
labelled second antibody, anti- to the first.

In another embodiment, a competition assay could be
performed between the sample and a labelled FABP or a

30 peptide derived therefrom, these two antigens being in
competition for a limited amount of anti-FABP antibody
bound to a solid support. The labelled FABP or peptide

could be pre-incubated with the antibody on the solid

- 6 -

phase, whereby the FABP in the sample displaces part of*
the FABP or peptide thereof bound to the antibody.

In yet another embodiment, the two antigens are
allowed to compete in a single co-incubation with the
5 antibody. After removal of unbound antigen from the
support by washing, the amount of label attached to the
support is determined and the amount of protein in the
sample is measured by reference to standard titration
curves established previously.

10 The label is preferably an enzyme. The substrate

for the enzyme may be colour-forming, fluorescent or
chemi luminescent .

It is highly preferable to use an amplified form of
assay, whereby an enhanced "signal" is produced from a

15 relatively low level of protein to be detected. One
particular form of amplified immunoassay is enhanced
chemiluminescent (ECL) assay. Here, the antibody is

preferably labelled with horseradish peroxidase, which
participates in a chemiluminescent reaction with luminol ,

20 a peroxide substrate and a compound which enhances the
intensity and duration of the emitted light, typically 4-
iodophenol or 4 - hydro xycinn ami c acid.

Another preferred form of amplified immunoassay is
immuno-PCR. In this technique, the antibody is

25 covalently linked to a molecule of arbitrary DNA
comprising PCR primers, whereby the DNA with the antibody
attached to it is amplified by the polymerase chain
reaction. See Hendrickson, E . R . et ml. , Nucleic Acids

Research 23, 522-529 (1995) or Sano, T. et a2 . , in

30 "Molecular Biology and Biotechnology" ed. Robert A.
Meyers, VCH Publishers, Inc. (1995), pages 458 - 460.
The signal is read out as before.

In a particularly preferred procedure, an enzyme-
linked immunosorbent assay (ELISA) was developed to

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detect H-FABP ±n serum. Since H-FABP is a marker for AMI
as well, Troponin-I or CK-MB levels were assayed in order
to exclude any heart damage . As described in the
Example, these assays were assessed in serial plasma and
5 CSF samples, from patients lacking AMI and CJD, patients
with AMI , patients with dementia and patients with
confirmed CJD through autopsy. The sensitivity,
specificity and predictive accuracy for H-FABP in CJD
above a suitable cut-off level were all 100%. Thus, H-
10 FABP detection combined with the Troponin-I or CK-MB
assay provides a useful serum marker of CJD diagnosis or
brain damage .

The use of a rapid microparticle-enhanced
turbid i metric immunoassay, developed for H-FABP in the

15 case of AMI, Robers, M. et al . , "Development of a rapid
microparticle-enhanced turbidimetric immunoassay for
plasma fatty acid-binding protein, an early marker of
acute myocardial infarction", Clin. Chem. 44, 1564-1567
(1998) , should drastically decrease the time of the

20 assay. Thus, the full automation in a widely used
clinical chemistry analyser such as the COBAS™ MIRA Plus
system from Hoffmann-La Roche or the AxSYM™ system from
Abbott laboratories should be possible and applied for
routine clinical diagnosis of CJD .

25 The H-FABP or B-FABP can be measured by other means

than immunoassay. For example, the sample can be
subjected to 1 or 2-DE gel electrophoresis and the amount
of the FABP estimated by densitometric scanning of the
gel or of a blot therefrom.

30 The assay of the invention can be used together with

one or more other pre -mortem assays for the TSE ,
including specifically those assays described above .
Such combined procedures are particularly useful in
diagnosing BSE in cattle .

- 8 -

The following Example illustrates the invention.
EXAMPLE

Materials And Methods
Patients

5 The study population consisted of 3 age-and-gender

matched control patients (Control group) , 3 confirmed AMI
patients (AMI group) , 3 confirmed dementia patients
(dementia group) and 3 confirmed CJD patients (CJD
group) . The Control group included 2 men, mean age 66 ,

10 range 46-86 years, and 1 woman, age 63 years. The AMI
group included 2 men , mean age 65, range 40-90 years, and
1 woman , age 72 years. The dementia group included 2 men,
mean age 65, range 43-87 years, and 1 women, age 64
years. The CJD group included 2 men, mean age 68, range

15 62-74 years, and 1 woman, age 65. Blood and CSF samples
were collected for each patient of the CJD. Blood samples
were collected in dry heparin- containing tubes . After
centrifugation at 1500g for 15min at 4°C, tubes were
stored at — 20°C until analysis. Patients from the CJD

20 group underwent serial clinical evaluations by
neurologists in order to confirm CJD diagnosis. Patients
from the AMI group were admitted to the hospital with a
confirmed AMI (Troponin-I concentration >2ng/ml) . A
clinical evaluation was performed on all the patients

25 from the control group to exclude CJD and AMI.
Measurement of brain and heart H-FABP

H-FABP levels were measured in plasma by a sandwich
ELISA. A 96-well polystyrene microplate (NUNC) was coated
with lOOul/well goat anti human-FABP, detecting all

30 isoforms (Spectral Diagnosis HC, Ontario, USA), 20.4ng/ml
in caxbonate buffer 0 . 1M pH 9.6, overnight at 4°C. The
plate was automatically washed with PBS (15mM Na 2 PC>4-120mM
NaCl-2.7mM KC1 pH 7.4, Sigma) on a BioRad NOVAPATH™
washer. Every washing step was performed with fresh PBS.

- 9 -

Non-specific binding sites were blocked with 200ul/well
2% casein in carbonate buffer for 2h at 37 °C. After the
washing step, the samples were pipetted in duplicate at
lOOul/well. The plate was incubated 2h at 37°C. After the
5 washing step, lOOul/well of mouse anti-human Heart FABP
(clone 66E2, HyCult Biotechnology BV, Uden, Netherlands),
0.3ng/ml in PBS-1%BSA, were incubated for lh at room
temperature (R.T) with shaking. After the washing step,
lOOul/well of phosphatase-labelled anti-mouse

10 immunoglobulin (Dako, Denmark), 15ng/ml in PBS , were
incubated lh 30min at R.T. with shaking. After the
washing step, 50ul/well of phosphatase substrate,
1.5mg/ml para-nitrophenylphosphate in diethanolamine was
added and the samples were then incubated for 30min . The

15 reaction was stopped with lOOul/well 1M NaOH . Colour
development was measured with a microplate reader at a
wavelength of 405nm .
CK-MB and Troponin- 1 measurement

AMI was diagnosed by clinical evaluation and

20 Troponin-I and CK-MB measurements . Samples were
centrifuged at 1500g for 15min, and stored at -20 °C.
Serum CK-MB and Troponin-I levels were determined using a
fluorescent microparticle enzyme immunoassay (MEIA) with
an automated chemical analyser AxSYM™ system (Abbott

25 Laboratories, Abbott Park, II*, USA). The rate of
formation of fluorescent products was directly
proportional to the amount of Troponin-I in the sample.
The detection limit for Troponin-I was 0.3ug/l. CK-MB
measurement is proportional to the amount of fluorescent

30 probes and the detection limit was 0.7pg/l.
Statistical analysis

H-FABP levels were expressed in optical densitometry
(OD) values either as mean ± SD or as median and inter-
quartile range . Troponin-I and CK-MB levels were

- 10 -

expressed in concentration units (ngVml) . The non-
parametric Mann-Whitney CJ-test and Kruskal-Wallis H-test
were used to compare in plasma H-FABP , Troponin-I and CK-
MB concentrations between groups. PRIS^ M software was
used to elaborate box/whisker and scatter plots. The 95%
confidence intervals (CI) and Receiver Operating
Characteristic (ROC) curves, defined by Analyse-it™
software for Microsoft EXCEL™ , were used to assess the
discriminatory time point of the indicators. See Murphy ,
J.M. et al. , "Performance of screening and diagnostic
tests' 1 , Arch. Gen. Psychiatry 44, 550-555 (1987).

P<0.05 was considered statistically significant.
Results

Clinical characteristics

Patients from the CJD group were given a complete
clinical evaluation. CJD was finally diagnosed with the
help of brain immuno -histology after autopsy. Patients
from the Control group were admitted to hospital and CJD
and AMI were excluded by clinical evaluation.

Patients from the AMI group were admitted to the
hospital with confirmed AMI with high Troponin-I levels
(>2ng/ml) .

Assay results are shown in Table 1 below.

Assay
type

Control

Group

plasma

AMI

Group

plasma

Dementia

Group

CSF

CJD

Group

plasma

CJD

Group

CSF

H-FABP
median
(25-75%)
OD, 405 nm

0.25

(0.23-

0.27)

2 .89
(2.70-
3.0)

O.20
(0.16-
0.31)

0.79
(0.74-
0.86)

0.46

(0.38-

0.54)

Troponin-1
median
(25-75%)
IU ng/ml

(0.0-
0.0)

(50-359)

(0.0-0.2

(0.0-0.2)

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H-FABP plasma levels (OD measurement) in the AMI
group were significantly higher than the respective level
in the Control group (Table 2) . The AMI group had a H-
5 FABP median level (range 25-75%) of 2.89 (2.70-3.0) while
the Control group had a level of 0.25 (0.23-0.27) . The H-
FABP plasma level in the CJD group was between the slopes
of the AMI and the Control groups . H-FABP median (range
25-75%) level in the plasma CJD group was 0.79 (0.74-

10 0.86). The sensitivity, specificity, and predictive
accuracy of H-FABP levels beyond the cut off value of
0.30 were 100%, 100% and 100% respectively. To confirm
differences in H-FABP concentrations between AMI and
Control groups, Troponin-I was assayed. In addition, in

15 order to discriminate AMI and CJD, they were also assayed
on CJD samples . The Troponin-X concentration was measured
in each group. Troponin-I concentration in the AMI group
was significantly (p>0.01) higher than in the Control
group .

20 Discussion

The above results indicate that H-FABP is a
potential marker for CJD diagnosis. Since H-FABP was
presented as a marker of acute myocardial infarction a
few years ago, CJD and AMI had to be discriminated by

25 another AMI biochemical marker such as Troponin-I or CK-
MB. After the discrimination of AMI for CJD patient, the
serum as well as the CSF H-FABP concentration could be
used as a specific marker of CJD.

In the present study, H-FABP assay allowed a

30 sensitivity, a specificity and a predictive accuracy (OD
response > 0.30) of 100%. These values were significantly
higher than those of 14-3-3 protein for detection of CJD
as the three dementia patients were positive after
immunoblotting detection. The specificity of 14-3-3 is

- 12 -

not limited to CJD but includes also Alzheimer's
dementia , cerebral complications from head injury and
some other forms of dementia.

Acute myocardial infarction is diagnosed with the
5 help of biochemical marker assays such as cardiac
Troponin-I, Creatine-Kinase MB, myoglobin and recently H-
FABP assay. The H-FABP level for CJD could interfere
with AMI and discrimination between AMI and CJD was made

with the use of other AMI markers .
10 *****

Each of the above cited publications is herein
incorporated by reference to the extent to which it is
relied on herein.

The following claims define some important
15 embodiments of the invention, but should not be construed
as detracting from the generality of the concepts
hereinbefore set forth.

~ 13 -

CLAIMS

1. A method of diagnostic assay for a transmissible
spongiform encephalopathy <TSE) or the possibility
thereof in a sample of body fluid taken from a patient
suspected of suffering from the TSE / which comprises
determining the concentration of heart or brain fatty
acid binding protein (H-FABP or B-FABP) in the sample.

2 . A method according to Claim 1 , wherein the subject
is a human and the concentration of H-FABP is determined
in a first assay, whereby a positive result indicates
either a CJD or acute myocardial infarction, and which
further comprises carrying out a second diagnostic assay,
for acute myocardial infarction {AMI ) only, whereby a
positive result in the H-FABP assay and a negative result
in the assay for AMI indicates that the patient is or
might be suffering from a CJD .

3 . A method according to Claim 2 , wherein the assay for
AMI comprises determining the concentration of troponin-1
or creatine kinase MB in plasma.

4 . A method according to Claim 1 , 2 or 3 , wherein an
antibody to H-FABP is used in the assay for H-FABP.

5. A method according to Claim 4, wherein the subject
is a human patient and a mouse anti-human FABP monoclonal
antibody is used.

6* A method according to any Claim 4 or 5 , wherein the
assay for H-FABP comprises a sandwich ELISA.

7 . A method according to Claim 1 , wherein B-FABP or an
antibody thereto is used without any assay for AMI in
combination therewith .

8. A method according to any preceding Claim, wherein
the H-FABP or B-FABP assay is carried out on a blood or
serum sample .

% Office I

Application No:
Claims searched:

GB 0005683.8
All

Examiner:
Date of search:

INVESTOR fN PEOPLE

Dr Rowena Johnson
10 August 2000

Patents Act 1977

Search Report under Section 17

Databases searched:

UK Patent Office collections, including GB, EP, WO & US patent specifications, in:
UKCl(Ed.R): GIB (BAE)

Int CI (Ed.7): G01N 33/543, 33/577, 33/68; C07K 14/47, 14/775

Other: ONLINE: WPI, JAPIO, EPODOC, TXTE, MEDLINE, EMBASE, SCISEARCH
BIOSIS, CAPLUS

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Full text of "USPTO Patents Application 10695194"

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